Method of correcting last models



Dec. 7, 1943. O s, PORTER ETAL 2,336,034

METHOD OF CORRECTING LAST MODELS Ofigihal Filed June 26 1941 2 Sheets-Sheet l aka 5Z5. ii

Dec. 7, 1943. o. s. PORTER EI'AL 2,336,034 METHOD OF CORRECTING LAST MODELS- Original Filed June 26, 1941 2 Sheets-Sheet 2 Patented Dec. 7, 1943 METHOD OF CORRECTING LAST MODELS Oscar S. Porter, ,Shrewsbury, and Leo A. Carroll, Lynn, Mass, assignors to United Shoe Ma.- chinery Corporation, Flemington, N. 3., a corporation of New Jersey Original application June 26, 1941, Serial No. 399,952. Divided and this application March 25, 1943, Serial No. 480,504

6 Claims.

This invention relates to model making in connection with the manufacture of lasts and is disclosed herein with reference to improved methods of correcting the bottom profiles of last models.

Style and foot fitting standards require that there be no Variation as to certain characteristics of lasts regardless of their size or width. For example, all lasts in a series of the same style should have the same heel height and toe spring. These requirements give rise to a difliculty in last making because of the well-known fact that the grading mechanism commonly used in last lathes is substantially pantographicin its action, multiplying all perpendicular distances from the grading axis by a factor which is constant throughout the turning. This causes a variation in the bottom profile of an enlargement or diminution of the model as compared with that of the model. That is, the toe tip beingsubstantially on the turning axis is reproduced correctly; but the heel drops a certain amount, and the ball drops (absolutely) more than any other point on the bottom since it is farther below the turning axis than any other point. t

The resulting variation in the bottom profile of the model is observable by holding the model with its forepart resting on a plane surface so that its heel height is correct or so that its forepart treads properly. In the first case, the variation is indi- .cated by an exaggerated toe spring (the vertical distance from the tread surface to the toe tip). In the second case the variation is observed as an excessive heel height. Actually the total variation is a combination of one in the wedge angle and another in the toe spring of the last model. To make a complete series of lasts, it is therefore common practice to provide a series of modelsin sufficient number that the above-mentioned variatiofis in lasts turned from the models will be negligible.

In making a model, it is customary to use a correct model in a last lathe to produce as accurately as possible by this method, considering the difficulties outlined above, an approximate enlarge- 7 its girth is a minimum. A similar cut is made in the model through the top of the cone, toward thebottom of the model but not through it, on a section which is substantially perpendicular to the bottom of th model at the forward edge of the heel plate or heel seat of a last corresponding to the model. Thetoe and heel portions of the model are thus partially separated from its mid portion and are capable of being moved, usingthe uncut sections of the model as hinges, so as to correct the toespring and wedge angle.

Holes are next drilled transversely of the kerfs mentioned above to receive fastenings which upon being driven are intended to hold the toe and heel portions of the model in their corrected relation with respect to the mid portion of the model. It is impracticable to maintain by hand the desired relation between the'portions of the last when these holes aredrilled, with the result that when a fastening is driven to correct the model, that part of the hole which is in one portion of the I model is moved out of alignment with the other part of the holein the other portion of the model, thus causing a binding action on the fastening which may prevent it from being driven to the extent necessary to efiect the required correction .of the model. Moreover, it is desirable that the movement of the toe and heel portionsof the model necessary-to make the corrections in question shall not result in their lateral surfaces adjacent to the keris becoming misaligned or discontinuous, since in such a case the swing of the model would be affected and the removal of material from the sides of the model necessary to make them smooth and continuous would reduce the size of the model in the area affected. This last-mentioned difficulty is minimized if the above-mentioned kerfs are made so that the bottoms of the kerfs are substantially parallel to the bottom of the model, or, in other words, are

perpendicular to the same given plane, but this ,result cannot be obtained accurately or approximated consistently when, as is the common practice, the-model is positioned with respect to the saw entirely by hand. v

The invention contemplates broadly the accurate control of each of the above procedures, namely, the formation of 'kerfs in ,a model to be corrected, the bottoms of which are to be -per- ,pendicular to th same plane and oa el ol o the bottom of the mod hthe position n and hol n of the toe and iheolpo t ohs o th mode re tively to i s mid po t on s a to ovide t P er bottom p ofi e and ho asten n to et .of a l the port ons of, the model ihr ho rrectedrelation. f

Accordingly, the invention in one aspect proadapted to rest on the table of the saw, the bottom of the model being perpendicular to the guiding surface of the holder. Thus, regardless of the angular relation of the planes of the kerfs to each other, the bottoms of the kerfs will be parallel to the bottom of the model.

Another important step in the method 'probers I0, l2, has a central run extending heightwise of the mid portion of the model, this run of the member H] being provided with a row of spaced holes 2'! any one of which is adapted to receive a rod 28 having a knurled head 30 on its upper end, the lower end of the rod being threaded into one hole of another similar row of holes 29 in the central run of the member l2. The rod 28 is perpendicular to both of the members I and I2 and is adapted to be received in a jig hole drilled transversely through the mid portion of the model 26 to provide a positioning surface parallel to its bottom and also perpendicular to the longitudinal axis of the model. Thus, when the device rests on the table 22 lines extending heightwise of the bottom of a model mounted vided by the invention consists in relatively mov H ing the toe, heel and mid portions of the model, which are partially separated from each other by the kerfs referred to above, to correct the bottom profile of the model and then holding these portions of the model in their corrected relation to facilitate both the gaging of the model in order to determine when the desired relation between parts of the model has been reached, and the final fastening together of the parts ofthe model in this relation.

In the latter aspect the invention further contemplates both the formation of bores or holes to receive fastenings for rigidly connecting the parts of the model and the driving or setting of fastenings in the bores while the parts of the model are held in their corrected relation or, in other words, while the partially separated'portions are maintained in their adjusted positions.

Thus, the above-mentioned shortcomings of the prior methods of correcting models by hand are avoided by the practice of the'present invention since the correct relation is maintained between the model and saw when the kerfs are made and also between the surfaces or parts of the model throughout each stage in the correction of the model.

The above and other aspects and features of the invention will be better understood from the following description of an illustrative embodiment thereof taken in connection with the accompanying drawings, in which,

Fig. 1 is a View in perspective illustrating a last model correcting device and its use in the method in forming kerfs in the model; i

Fig. 2 is a sectional plan view of the device illustrating its use in correcting the wedge angle and toe spring of a model; and

Fig. 3 is a sectional view on a reduced'scale taken on the line III--III of Fig.2.

The illustrated device for use in practicing the present method comprises a frame having parallel upper and lower members I0, l2, and verticall disposed struts l4, l6 and I8, the ends of the struts being rigidly connected by screws 20 to the members If! and I2. The lower surface of the member [2 acts as a guiding surface for the device and is adapted to rest on a saw table 22 through which a saw blade 24 of the band type is adapted to move perpendicular to the table 22. V f' In carrying out the method, a last model 26 to be corrected is secured in the device as will be described below so that when the model is presented to the saw 24, with the member l2 then resting on the table 22, the bottom of the kerf made by the saw will be substantially parallel to the bottom of the model. Each of the'mem on the rod 23 are substantially parallel to the direction of movement of the saw blade 24. Hence, the bottoms of kerfs made by the saw blade when the device is resting on the table 22 will be parallel to the bottom of the model. A clamp 32 is arranged to cooperate with the rod28 to hold the mid portion of the model firmly in the illustrated device. The clamp 32'extends lengthwise of the ridge of the cone of the model, and carries pads 34 adjacent to its ends which are adapted to engage the ridge of the cone of the model at spaced points. The clamp 32 is mounted on a pair of guide rods 36 (Fig. 3) the outer ends of which are connected by a plate 38, the rods being mounted to slide lengthwise thereof in the strut I6. The clamp 32 is moved toward and away from the model by a screw 40 which is threaded in the strut IS, the inner end of the screw 49 being adapted to rotate freely in the clamp. Assuming now that a model to be corrected has been properly drilled as described above to receive the rod 28, the model is mounted on the rod and the screw 40 is operated to clamp the model securely in the device. The model is next presented to the saw 24 so as to form a kerf 42, located before the mid portion of the model substantially where its waist measurement is taken (section of minimum girth), and extending transversely and heightwise of the model. This kerf terminates short of the upper surface of the model so as partially to separate the toe end of the model from the mid portion thereof and to permit the toe portion of the model to be moved, using the narrow and springy uncut section of the model as a hinge, in order to correct the toe spring of the model. A similar kerf 44, to permit a correction to be made in the wedge angle of the model, is out toward (but not through) the bottom surface of the model through the top of the cone, the plane of this kerf passing through-the bottom of the model substantially perpendicular thereto along a line corresponding to the forward edge of the heel plate or heel seat of a last corresponding to the model. As clearly shown in the drawings, the central runs of the members Ill and I2 are so shaped and arranged as to occupy only a part of the space included between the planes of the kerfs 42 and 44, thereby topermit unobstructed access to the saw 24 of the portions of the model to be cut. The frame members 10 and 12 also comprise rear runs connected to the central runs below the bottom of the model, and extending heightwise and rearwardly between the kerf 44 and the rearmost point of the bottom of the model. The shape and arrangement of the runs of the members I0 and I2 insures unobstructed visibility, from one side of the model, of points along its bottom at the heelend,jbreast line, ball and toe 'end whereby the relation of -;me.=;e points to a gage or template for testing thebottoin profile of themodel can readily be observed. I v I? After the kerfs-fiZ and 44 have been made, as described above, the toe and heel portions of the model, in accordance with the present method, are moved relatively to the'mid portion of the model to correct its toe spring and wedge angle, this correction being indicated in Fig. 2 by the angle betweenthe full anddotted lines indicating the bottomprofie of the'toe andheel portions of the model in their corrected and original positions respectively.

The toe spring of the model is corrected by adjusting a screw 45 threaded in a slide 48., and carrying at its lower end a pad 55. The pad is connected to .the screw by a ball and socket joint which permits the pad to seat itself on whatever portion of the model it engages. The slide 48 is adapted to be moved lengthwise of the last in a slot 5| formed in the strut IE to bring the pad 50 over the toe end of the model regardless of its length.

Another screw 52 at the heel end of the device for correcting the wedge angle of the model is threaded in the strut l4 and is operable to move a bar 54 toward or away from the heel portion of the model. The screw 52 is arranged to rotate freely in the bar 54 and is held in the latter by a in 55 which is fixed in the bar 54 and received in a peripheral groove formed in the screw 52. A pair of screws 58 fixed on each end of the bar 54 are received in slots 59 in the frames l0 and I2, thereby to guide the bar 54 axially of the screw 52.

Ordinarily, in the use of the illustrated device in carrying out the method, the screws 46 and 52 are set up so as to cause the open ends of the kerfs 42 and 44 to be closed, although if a lesser movement of the toe and heel portions of the model is adequate to provide the required correction, the operator may make a corresponding smaller adjustment. If, upon measuring the model, the toe spring and wedge angle are found to be correct, the toe and heel portions of the last ar next permanently secured to the mid portion while they are held in their corrected positions by the screws 46 and 52. If the measurement of the model indicates that the correction permitted by closing a kerf formed by only one saw cut is inadequate, the model is again presented to the saw, the original kerf being closed completely or to a lesser extent depending upon the required degree of correction. It thus is possible in the present method by the use of the illustrated device to increase the width of a kerf by predetermined amounts depending upon whether the original kerf is partially or entirely closed before the second cut is made. this procedure the operator is enabled to cut away such an amount of the model that when the required correction is made portions of the model at opposite sides of the kerf will be firmly seated on each other thereby insuring rigidity in the connection between the mid portion of the model and its toe or heel portions.

The permanent fastening of the end portions of the model to its mid portion is also effected, in

accordance with the method herein disclosed,

while the partially separated portions of the model are held in their corrected relation or, in

other words, while they are maintained in their adjusted positions. The first step in this procedure consists in drilling holes adapted to receive screw fastenings, the heads of which are As a result of seated in the toe-and heel portions of'the'model and the threaded portions of which engage the mid portion of the model. As herein illustrated each screw'fastening 60 is inserted in a bor or hole the different sections of which in the different portions of themodel are coaxial. Each bore comprises a section 6| large enough to accommodate the head of the fastening 60, a somewhat smaller section 52 adapted to receive the shank of the fastening, this section extending through the kerf. A third and still smaller section 64 of the bore is formed in the mid portion of the model so as to facilitate the setting of the fastening and to avoid splitting of the model.

It will now be understood that because the partially separated portions of the model are held in their corrected relation-or adjusted positions when the bores 62- and 64 are made and the fastenings '60 are driven, these bores can readily be formed in exact coaxial relation and of such size as closely to receive the fastenings, thereby eliminating any tendency for th fastenings to become jammed as they are driven and insuring a rigid connection between the portions of the model.

The novel last model correcting device disclosed therein as particularly adapted for use in carrying out the present method has not been claimed herein since it forms the subject matter of a copending application Serial No. 399,952, filed in our names June 26, 1941.

Having described our invention, what we claim asf new and desire to secure by Letters Patent of the United States is:

1. The method of correcting last models which consists in cutting a transversely disposed kerf from one surface of a model to a point short of the opposite surface thereof so as partially to separate an end portion of the model from the mid portion thereof, moving the partially separated portions relatively to each other to correct the model, and fastening the portions against relative movement while they are maintained in their adjusted positions.

2. The method of correcting last models for toe spring which consists in cutting a transversely disposed kerf from the bottom surface of a model to a point short of the top surface thereof so as partially to separate the toe portion from the mid portion thereof, moving the partially separated portions relatively to each other to correct the toe spring of the model, and. fastening the toe and mid portions against relative movement while they are maintained in their adjusted positions.

3. The method of correcting last models for wedge angle which consistsin cutting a transversely disposed kerf from the top surface of a model to a point short of the bottom surface thereof partially to separate the heel portion from the mid portion thereof, moving the partially separated portions relatively to each other to correct the Wedge angle of the model, and fastening the heel and mid portions against relative movement while they are maintained in their adjusted positions.

4. The method of correcting last models for toe spring and wedge angle which consists in cutting longitudinally spaced and transversely disposed kerfs from the top and bottom surfaces of a model toward, but short of, the opposite surfaces so as partially to separate the toe and heel portions from the mid portion of the model, moving the said portions with respect to each other to correct the toe spring and wedge angle of the model, and fastening said portions against rela: tive movement while they are maintained in their adjusted positions.

5. That method of correcting last models which consists in cutting a transversely disposed kerf from one surface of a model to a point short of the opposite surface thereof with the bottom of the kerf extending substantially parallel to the bottom of the model, thereby partially separating an end portion of the model from the mid 10 portion thereof, moving the partially separated portions of the model relatively to each other to correct the bottom profile of the model, and fastening said portions against relative movetransversely disposed kerfs from outer surfaces of a model to points short of the opposite surfaces thereof with the bottoms of the kerfs extending substantially parallel to the bottom of the model and perpendicular to a predetermined plane, thereby partially separating the end portions of the model from the mid portion thereof, moving the partially separated portions relatively to each other to correct the bottom profile of the model without interrupting the continuity of the outer surfaces of the model through misalignment of the lateral surfaces thereof adjacent to the kerfs, and fastening said portions against further movement relatively to each other while maintaining ment while maintaining them in their adjusted 15 them in their correct adjusted positions.

positions.

6. That method of correcting last models which consists in cutting longitudinally spaced and OSCAR S. PORTER. LEO A. CARRELL. 

